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Multiple vs single bass drivers and room effects

tw99

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#1
Assuming a 2.0 stereo pair of tower speakers, is there any advantage from a room interaction perspective from having multiple bass drivers vs a single one ? I'm thinking of something like a Kef R7 which has a woofer above and below the Uni-Q driver, or even the R11 which has two above and two below. Would these layouts typically produce more even results than a conventional layout with a single bass driver, because the floor/ceiling bounce effect will be slightly different for each individual driver ? Or is it just another "it depends on so many factors" thing ?
 

pozz

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#2
Potentially. If drivers are putting out the same frequencies they will start resembling line sources, which makes them more directional.

You still have to deal with room interactions, so all the regular caveats, problems and solutions will apply.
 

Kvalsvoll

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#3
Larger radiating area is always better for bass, but the difference is larger in the mid-low midrange. In many cases, the difference will not be significant at low frequencies, part from the larger capacity of course.

This sort of configuration with more small drivers arranged vertically will give vertical directivity control in the midrange. But the end result may not necessarily show up as improved smoothness in frequency response, that depends on the position of the individual drivers relative to the floor boundary and how the crossover is designed. Going from one to just 2 drivers may give perceived better impact in the lower midrange.
 

valerianf

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#4
I would prefer to buy a speaker equipped with a high end midrange than a speaker equipped with multiple low end midrange drivers. It is the most important frequency range for music details.
Same remark for the woofer.
 
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FeddyLost

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#5
because the floor/ceiling bounce effect will be slightly different for each individual driver ?
In theory it might help to reduce floor/ceiling bounce dips.
But I'd think about possible excitation of room modes with distributed bass drivers.
If your room is troublesome, I'd estimate pressure zones and see if drivers will be located exactly there. Floor bounce dip is not a big deal compared with boomy bass from modes.
 

digitalfrost

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#6
Potentially. If drivers are putting out the same frequencies they will start resembling line sources, which makes them more directional.
Okay but at these wavelenghts, in normal sized rooms, this won't matter right?
 

pozz

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#7
Okay but at these wavelenghts, in normal sized rooms, this won't matter right?
I don't think woofers in three/four way towers are putting out enough bass for there to be any significant effect on mode excitation. If we were talking subwoofers the height differences and multiple drivers would be important.
 

Mnyb

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#8
But there have been others on this forum that suggested that for example revel saloon2 row of 3 bass drivers helps with some SBIR effects ?
At least one of the drivers get very close to the floor .

Question if you have only one bass driver in the speaker and fairly low XO (3 or 4 way) would it not be beneficial the have the driver close to the floor , Ive seen speakers with this kind of solution , there must be a reason for it ?
 

FeddyLost

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#9
I don't think woofers in three/four way towers are putting out enough bass for there to be any significant effect on mode excitation
If you're right, how exactly i.e. 5" monitors will excite anything in room?
I see no difference between 6" woofer and 12" woofer if they play same modal resonant frequencies...

Ive seen speakers with this kind of solution , there must be a reason for it ?
For sure. Half-space reinforcement, BIR dip moving up, but you need very low crossover point, which is not cheap in passive.
So, it's not very popular.
 

pozz

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#10
If you're right, how exactly i.e. 5" monitors will excite anything in room?
I see no difference between 6" woofer and 12" woofer if they play same modal resonant frequencies...
It's the total energy output that matters. Below 100Hz a 6" driver will hit limits very fast. Multiple 6" drivers on towers don't produce enough bass output each to avoid any of the usual room problems.

The only useful distinction between towers and other speakers is bass extension and driver summation distance. You will still have to EQ and find the best speaker/listening position. Towers won't make the latter any easier from an acoustic standpoint.
 

Mnyb

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#11

steve59

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#12
Interesting. I thought Kef moving to 6.5'' woofers was questionable especially in their reference line since one would expect full range at those prices. I had a pair of really affordable speakers in the 80's Fischer xp95c with 15'' woofers and while fidelity was suspect when listening to fm radio those speakers would pressurize the room when someone on the other end of the broadcast would close a door. Fascinating, Either fm stations no longer open and close doors during live broadcasts or my megabuck full range, multiple driver woofs can't compete.
 
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